An elementary particle with an unusually long lifetime or, from the Heisenberg uncertainty principle, with an extremely narrow width Γ = 86.6 ± 6.0 keV, and a large mass m = 3096.93 ± 0.09 MeV. It is a bound state containing a charm quark and an anticharm quark. The discovery of the J/psi particle is one of the cornerstones of the standard model.